1. Field of Invention
The present invention relates to an image forming method in which an image is formed by discharging an ink composition, and an ink composition used for the same.
2. Description of the Related Art
In recent years, as a result of ever-increasing demand for the protection of resources, protection of the environment, enhancement of operational stability and the like, the conversion of inks into aqueous products has continued to proceed. The product qualities demanded from aqueous inks include fluidity, storage stability, glossiness of film, clarity, coloring ability and the like, as in the case of oil-based inks.
Since most pigments have significantly deteriorated aptitude such as pigment dispersibility with respect to an aqueous vehicle in comparison with the case of an oil-based vehicle, sufficient quality cannot be obtained by conventional dispersion methods. The use of various additives such as, for example, an aqueous pigment dispersion resin or a surfactant has been studied heretofore. However, an aqueous ink comparable to an oil-based ink which has existing high quality and sufficient aptitude such as pigment dispersibility has not been obtained.
With respect to these circumstances, for example, there is disclosed an aqueous ink composition which contains polymer particles and a colorant having a water-insoluble polymer coated thereon as a color material (for example, see Japanese Patent Application Laid-Open (JP-A) No. 2001-329199). Further, an aqueous inkjet recording liquid containing a pigment and colloidal silica, an ink composition containing a resin emulsion and an inorganic oxide colloid, and the like are disclosed (for example, see JP-A No. 9-227812, JP-A No. 9-286941, and Japanese Patent No. 3550637), and a good image can be formed by including colloidal silica or the like from the viewpoint of abrasion resistance, color unevenness, clarity, and the like.
Further, there is disclosed an aqueous ink composition which prevents the elution of glass, silicon, silicon oxide, or the like in contact with an ink, by using the zeta potential of the ink and the zeta potential between a member and a color material (for example, see JP-A No. 2003-165936).